1. Field of the Invention
The present invention relates to a method and apparatus for displaying a moving image on a display device.
2. Description of the Related Art
If a display has a memory function and light is emitted at a relatively stable brightness, since a pixel on the display surface emits light until the memory of the pixel is rewritten with new image information of a next frame, the display is called a xe2x80x9chold-typexe2x80x9d of a display. Such a hold-type of a display includes a liquid crystal display (LCD).
However, conventionally a hold-type display has well known shortcomings and failings such as blurred contours and jerkiness wherein movements become xe2x80x9cjerkyxe2x80x9d (e.g., abrupt) when a moving image is displayed on a hold-type of a display (e.g., see pp. 19 to 26 of Shingaku Gihou EID96-4 (1996-06)).
In the article referenced above, it is shown that these error conditions are improved by using a shutter function of 50 percent or less than that of an aperture rate. The shutter in the article is referred to as a display shutter while its details are not described.
Further, Japanese Published Unexamined Patent Application No. Hei 9-325715 discloses that a shutter using polymer dispersed liquid crystal (LC) and a ferroelectric LC is set between a display and a user.
Additionally, when displaying a moving image on a personal computer, high speed processing is achieved by using a graphic device with a hardware overlay function (e.g., see U.S. Pat. No. 5,696,527, U.S. Pat. No. 5,592,236, and U.S. Pat. No. 5,583,536). However, there is no instance wherein a combination of an overlay function and the above-mentioned shutter function is considered.
In view of the foregoing and other problems of the conventional method and structures, it is, therefore, an object of the present invention is to enable a moving image to be clearly displayed on a hold-type of a display, such as an LCD, by setting a shutter function in an overlay processor.
In a first aspect of the present invention, a computer which has a display device for displaying a moving image, includes a memory with an on-screen area for storing display image information and an off-screen area for storing image information of the moving image. The on-screen area includes a memory section area used as a display area for the moving image and for storing predetermined key color information (e.g., a color used infrequently, such as a very dark blue, almost black, etc.).
The computer further includes a data reading circuit (a video RAM (VRAM) reading circuit 301) for reading the display image information from the on-screen area and the image information of the moving image from the off-screen area. A shutter circuit is provided for outputting the image information of the moving image from the data reading circuit or predetermined color information (e.g., black) by a predetermined frame cycle (for instance, for each frame). A key color detecting circuit is provided for determining whether or not the read display image information is key color information. A selector circuit is provided for outputting to the display, an image signal corresponding to the display image information if the read display image information is not the key color information, or for outputting a signal corresponding to an output of the shutter circuit if the read display image information is the key color information.
The combination of these features will have the same effect as having a shutter function of 50 percent or less than that of an aperture rate because black or image information of a moving image is displayed being switched for each frame in an area of the screen displaying the moving image.
With this arrangement, by setting a shutter function in an overlay processor, a moving image can be displayed clearly on a hold-type of a display such as a liquid crystal display.
The present disclosure relates to subject matter contained in Japanese Published Unexamined Patent Application No. Hei 10-204610, filed Jul. 21, 1998, which is expressly incorporated herein by reference in its entirety.